How, 60 years on, can there be anything fresh left to think, write or research about the Holocaust? No scar on the human psyche has been more exhaustively probed, no wound more constantly exposed. Yet this new work, from a couple of young German historians, is still a revelation. It sidelines Hitler, Himmler and the hateful rest, and looks beyond - at the civil servants who devised the policy and the academics who gave it credibility.

Here was the underpinning of annihilation, these doctors and professors its true architects, learned men and women who, after 1945, simply went back to their university desks and carried on, as though million upon million of murdered Jews, gypsies and Russians had nothing to do with them.

And the really chilling conclusion is that they were not zealots, madmen or uniquely evil. They didn't turn on the taps in the gas chambers. They wrote dry reports and analyses. They were, for the most part, demographers, town planners, economists; respected chaps from respected institutions. Many of them didn't dream of joining the Nazi party. They valued their 'academic independence' too highly.

Could it (perennial question) happen again? Wince and say of course. Not just because of anti-Semitism, but because the world of making things work remains in the hands of the professionals, interested in pay and job opportunity and career advancement. Welcome to the dark side of the office.

What Aly and Heim are arguing is the most mundane of horrors. Take a country like Germany in the Thirties, an older generation of academics and administrators hanging on through the disillusion of Weimar, a new generation chafing for its turn. Take a series of problems dogging the planners of the time.

How could Europe, in peacetime, feed itself and reduce its fatal dependence on supplies from an unpredictable outside world? How, in wartime, could survival be guaranteed? Ask the experts: always ask the experts. There the demographers had it. They had their formulas for the optimum number of agricultural labourers needed to till the land and feed the industrial cities. But 'rural overpopulation', especially in eastern Europe, was a sticking point. Clearly, potentially productive peasants, say Poles, needed to be moved off the land and into the factories. Cities like Warsaw were overpopulated, too, with 'useless mouths' (the old, the criminal, Jews). Clear the cities of that incubus, restore a decent, productive balance on the land and - bingo! - it would all come up roses.

The argument, for the most part, was couched in economic and sociological jargon. It could be as clinically detached as calculating the number of trained firemen required to man a night shift. Fine percentages were the order of the day. Carve off this chunk of the Soviet Union, leave Russian cities without any visible means of feeding themselves, and X or Y per cent of demand could be reasonably fulfilled.

Massive population shifts? Why not? They were a commonplace in early twentieth-century Europe. If clearances precisely organised would make a greater Germany at the heart of a greater Europe, where did any problem lie? The Nazis offered their own particular answers. They pushed away normal restraints, especially after the failure of a plan to ship thousands of these useless mouths to Madagascar. They deemed that genocide, not just of Jews, but of millions of Russians left callously, sentiently to starve, was an option of tolerable resort for the detritus of society. They made what happened possible.

But they did not devise the plans or advance the scientific rationale on which to build such possibilities. That honour belonged to people like Professor Konrad Meyer, director of the Institute for Agrarian Studies, for his work 'on the reconstruction of the eastern territories'. To Dr Gerhard Ziegler, for his help in Silesian regional planning. To his colleague Dr Fritz Arlt, sociologist and demographer, for the vision necessary to the development of Auschwitz concentration camp so efficiently close to Auschwitz new town, so that 'appropriate measures' might be taken in the construction of this new, model society.

Ziegler was soon back en poste after the war ended, planning regionally again, brandishing an honorary professorship from Stuttgart and (later) the federal government's Grand Cross of Merit. Meyer got a new job as a professor in horticulture and landscape design at Hanover. Arlt became head of the 'department for educational work and sociopolitical questions' at the Cologne Industrial Institute.

It wasn't, when they resurfaced, a case of the Germans going soft on their own. Some of these people got jobs in America. Some were hired by the British. They hadn't made the foaming speeches or ordered the executions. They had 'done' nothing. 'While there was dissent and friction between individual Nazi bigwigs, the experts inhabited a world characterised by a common technocratic culture of rational calculation, broad consensus, close personal ties and continuity.' They belonged to the same clubs, went to the same conferences. They were ordinary lives going on in extraordinary times.

Aly and Heim marshal their facts meticulously (and AG Blunden's translation is fluid and unobtrusive). This is not a racy or sensationalist read. To the contrary, especially for lack of an index, it is quite hard work. But there is never any question of stopping, of drawing breath, before the chronicle is over. After the drivel of Mein Kampf and the 'anti-intellectual' ravings of National Socialism's political heavy hitters, here are the intellectual boys in the backroom, applying science, deploying logic. 'Professionals and specialists' feeling free, at last, 'to turn their utopias into reality'.